Why does this happen?

Since much of the content on our web site is medically related, we need to make sure it's current. Old, out of date information is not helpful, and in some cases might actually be harmfull. For this reason, we expect publishers to periodically review the content of their web site to make sure it is all up to date.

In the old CMS, all pages were set to automatically expire after 18 months. When somebody edited that page, the timer would be reset for another 18 months.

In the new CMS, all content was imported with it's existing expiration date. This means that any content that was already expired was imported in an expired state. It also means that some pages might have expired since the migration, or will expire in the near future. We have not yet implemented a system to automatically reset the epiration date on content when edited, so even pages that are being activley maintained may expire. If this happens, you will need to reset the expiration date.

The web team are working on some improvements to the CMS to help identify expired pages more easily.